The present invention relates to a brake apparatus with a parking brake, that presses a friction member to a rotor by operating a piston provided at inside of a cylinder portion of a caliper, and has an automatic clearance adjusting mechanism with an overadjustment preventer, provided between the cylinder and the piston, for properly maintaining a clearance between the friction member and the rotor by the overadjustment preventing automatic clearance adjusting mechanism.
As a brake apparatus having an automatic clearance adjusting mechanism with an overadjustment preventer of a background art, for example, JP-B-05-074732 is known. The brake apparatus of JP-B-05-074732 comprises a ring piston in which a piston provided at inside of a cylinder portion is slidable at the inside of the cylinder portion, and a plug piston that slides at the inside of the cylinder piston for pressing a friction member. In the brake apparatus, the automatic clearance adjusting mechanism is provided with an adjusting nut brought into contact with the plug piston, a bearing for rotating to support the adjusting nut, an adjusting spindle screwed to the adjusting nut by a reversible screw, a one way clutch for hampering the adjusting nut from being rotated in one direction, and a ring-like member integral with the adjusting nut for preventing overadjustment.
In adjusting a clearance, by a hydraulic operation of the plug piston, the adjusting nut is extracted from the adjusting spindle, and in preventing overadjustment, the ring-like member is pinched by the two pistons by a pressing force by hydraulic pressure operated to the ring piston to hamper the adjusting nut from being pivoted. Further, there is provided a mechanical operating mechanism in which in operating the parking brake, the friction member is pressed to the rotor by being brought into contact with the plug piston while hampering the adjusting nut from being pivoted by the one way clutch via the adjusting spindle.
Further, according to a brake apparatus of JP-u-06-071348, in preventing overadjustment, an adjusting nut is pressed to a friction coupling portion coupled with a piston by hydraulic pressure operated thereto to thereby prevent the adjusting nut from being pivoted.
However, the brake apparatus having the automatic clearance adjusting mechanism with the over adjustment preventer of the JP-B-05-074732, needs constraining means of the ring-like member for hampering the adjusting nut from being pivoted in preventing overadjustment and the one way clutch for hampering the adjusting nut from being pivoted in operating the parking brake. Therefore, a number of constituting parts is increased and also integration thereof is complicated. Further, according to the brake apparatus of JP-U-06-071348, a path and a chamber under the atmospheric pressure provided for hydraulically operating the adjusting nut must be ensured. Therefore, working and layout thereof are laborious.